The present invention relates to an apparatus comprising a device and to a method for producing the apparatus comprising the device.
Electrical devices, for example semiconductor devices, are implemented on a semiconductor material or semiconductor substrate, for example silicon. Examples of devices of this kind are so-called BAW (Bulk Acoustic Wave) filters which are frequently operated as passive electrical RF (Radio Frequency) devices in the gigahertz range in electrical circuits. Thus, capacitive coupling either directly between individual conductive tracks or via an electrically conductive substrate material is frequently undesirable and to be avoided.
On the one hand, coupling among conductive tracks may be minimized by a skillful or suitable design of the pads and conductive tracks and a high-resistance semiconductor material may be used as a substrate or substrate material on which the electrical device is implemented so that capacitive coupling between the metal layers and/or conductive tracks via the substrate material can be prevented from occurring due to the high resistance. However using a lightly doped semiconductor material a voltage-dependent capacitance and/or substrate capacitance occurs between the metallic patterns in the device, such as, for example, the BAW filter, and the substrate. This voltage-dependent capacitance results from a surface field effect at a metal-insulator-semiconductor interface. This effect is known from MOS-transistors (Metal-Oxide-Semiconductor-transistors). Such a voltage-dependent substrate capacitance influences and/or disturbs the electrical performance when operating the device. Thus, voltage-dependent substrate capacitances should be kept low.